Almaty, Kazakhstan (CNN) -- Talks began Tuesday between six world powers and Iran over its controversial nuclear program for the first time in nearly eight months.

But the mood going into the negotiations was as bleak as the fog that hung over this snowbound Central Asian city.

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"I don't think tomorrow (Tuesday) is likely to be a day in which we can announce a great success," a diplomat participating in the negotiations told journalists on condition of anonymity on the eve of the first meeting.

Other officials were not so optimistic either.

Iran nuclear program under pressure How sanctions hurt Iran What will 2013 bring for Iran, Israel? What will 2013 bring for Iran, Israel? "Most probably, the negotiations in Almaty will fail," said Hossein Mousavian, who served as Iran's nuclear negotiator until 2005.

Iran has held several rounds of negotiations with the P5 plus 1, which comprises Germany and the five permanent members of the United Nations Security Council. The five members are the United States, France, Britain, Russia and China.

But since the delegation last met, Iran's uranium enrichment program has expanded in violation of the United Nations Security Council resolutions.

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At the same time, international sanctions crippling the Iranian economy have gotten tougher.

Iran insists it is only developing nuclear technology for peaceful energy needs. The nation's supreme leader repeated that message in a long speech on February 16.

"The Islamic Republic of Iran has not decided to build nuclear weapons and this decision is not because of America's concern. Rather, this decision is based on the belief that building nuclear weapons is a crime against humanity," Ayatollah Ali Khamenei said.

"If Iran had decided to build nuclear weapons, America would not have been able to stop the Iranian nation in any way," Khamenei added.

But a quarterly report published earlier this month by the International Atomic Energy Agency continued to cast doubt on Iran's nuclear program.

The IAEA said Iran had continued its production of 20% enriched uranium, though the majority of the uranium had been converted to fuel, which is not material that can be used for a weapon.

Iran installed new centrifuges, the IAEA reported. It has also refused to provide IAEA inspectors access to the Parchin military complex, which is suspected of housing a large containment vessel that could be

"The Agency is unable to provide credible assurance about the absence of undeclared nuclear material and activities in Iran, and therefore to conclude that all nuclear material in Iran is in peaceful activities," the IAEA concluded.

Since the last round of negotiations were held in Moscow in June, the United States, the European Union and the U.N. Security Council have continued to pile sanctions against Tehran, crippling the country's economy. Iran's oil exports have plummeted more than 50% as has the value of the rial, Iran's currency.

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Most recently, the United States and the European Union imposed sanctions restricting the sale of gold and precious metal to Iran.

Last November, Turkey's deputy prime minister confirmed suspicions among many economists that a surge in Turkish gold exports to Iran was basically an oil-for-gold trade to circumvent sanctions blocking Tehran from international electronic transactions.

Former Iranian nuclear negotiator Mousavian argued it would be impossible for both sides to agree to a deal, unless the P5 plus 1 offered relief from sanctions.

Western diplomats said they brought a new package of proposals to Almaty, but declined to comment on the specifics.

"We've put some proposals forward, which will hopefully help Iran show some flexibility," said Michael Mann, a spokesman for Catherine Ashton, the European Union foreign policy chief who is chairing the talks.

"What comes out of this meeting does depend very much on the Iranian reaction to what we propose," Mann added. "The onus is very much on the Iranians. They are of course in breach of U.N. security council resolutions and board of governance IAEA resolutions as well."

In a separate briefing, a U.S. official told journalists, on condition of anonymity, that the new package would include "some additional sanctions relief."

In his speech on February 16th, Iran's supreme leader argued that the P5 plus 1 countries, and in particular the U.S., were insincere when they talked about working toward a negotiated solution.

"This kind of negotiation does not serve any purpose. It will not reach any results," Khamenei said.

"They are not after genuine and fair negotiations. Rather, that they are pursuing the goal of making the Iranian nation surrender."

Analysts have suggested it may be difficult for the Iranian delegation to agree to any substantial compromise since Iran is gearing up to elect a new president in June.

Asked about this theory, the U.S. official told journalists elections "may constrain their political space."

But, the official added, "when it comes to the nuclear file, the decisions rest in the hand of the supreme leader and he is not going to change in June."

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